The present invention relates to a draft shield for a balance. The balance has a housing, and the draft shield comprises a base, a rear wall connected to the base, a front wall connected to the rear wall, at least two side walls, and a top cover. The invention further relates to a balance that is equipped with the inventive draft shield.
Draft-protection devices of the aforementioned kind are known, e.g., from EP-A-0 610 549, in which a draft shield can be releasably attached to the topside of a balance housing. However, the attachment requires that several different locking devices be provided in configurations that are compatible with the size of the respective draft shield that each locking device is designed for. As may be learned from the introductory part of the description of the aforementioned document, the only purpose of the attachment is to provide a secure connection of the draft shield to the balance housing, as compared to a draft shield that is only set down onto the top of the balance housing.
The object of the present invention is to simplify and thereby achieve cost savings in the manufacturing process of balances, particularly in cases where an assortment of different balances is to be manufactured and/or different versions of a draft shield are to be supplied for existing balances. A further objective of the invention is for the wall panels of the draft shield to be easily interchangeable, so that the wall panels themselves as well as the guide elements arranged in the draft shield are easy to clean.
To solve this problem, the invention provides a draft shield with a base comprising a locking device that is engaged in the balance housing and releasably connects the draft shield to the balance housing.
The inventive concept provides for a modular construction using a small number of parts that are produced in large quantities, i.e., economically, while making it possible to offer a range of different types of balances or to adapt a given type of balance to a wide range of different requirements. This obviates the need for different types of locking devices needed for each different size and configuration. Although it might be possible to work with as few as two types of locking devices, each of a given standardized configuration and standardized size, it is preferable to have only one single type of locking device.
In a preferred embodiment, the concept of a single type of locking device is put into practice by providing a latch slide that is movably guided in the bottom of the base so that it can be brought from a released position to a locked position. The latch slide has at least one projection or at least one cutout for the engagement with at least one matching recess or projection of the balance housing. It is to be understood that either the projection or the associated cutout or recess may be provided on the part of the draft shield or on the part of the balance housing, given that these elements are complementary to each other.
In contrast to an essentially known bayonet connection, the preferred way of releasing or fastening the draft shield is by means of a locking device that slides back and forth. This type of locking device provides an advantageous way of using draft shields of different geometric configurations depending on the desired application.
In most cases, a draft shield of this type is made of a polymer or other material that is susceptible to becoming electrostatically charged. Therefore, in order to avoid the build-up of an electrostatic charge, it is advantageous if the locking slide is made of an electrically conductive material, such as a metal.
In accordance with a further aspect of the invention, the problem described above is solved by providing the balance with at least one connector element for attaching an accessory module to the balance. In the case of a draft shield, it is advantageous for the balance to have at least one projection or, respectively, at least one recess in cooperative engagement with a corresponding part of the locking slide of the draft shield.
Concerning the static electricity that was mentioned above, the preferred countermeasure is to use an electrically conductive material, particularly a metal, for the projection or recess of the balance housing.
It is further beneficial, if the balance housing consists at least in part of a conductive material that is conductively connected or connectable with the electrically conductive projection or recess because a relatively large surface area of electrically conductive material is thereby made available to return the static electricity directly to the environment, provided that the atmospheric humidity is sufficient.
Also as an accessory module, either as an alternative or in addition to the draft shield, an attachment unit with electrical connections, e.g., a power supply, signal interface, A/D or D/A converter, may be connectable to the balance by means of the connector element.
According to a further aspect of the present invention, a draft shield is of a design that permits at least one of the walls of the draft shield to be brought from a closed position to a removed position. The concept may be carried out in a design of the draft shield where at least one of the walls is slidable from a closed position to a rest position and the slidable wall has a grip handle that protrudes towards the outside and is slanted at an angle from the vertical. This arrangement is based on the observation that, on the one hand, it makes the grip handle easier to grasp because it offers an approximately triangular free space that is conveniently accessible to the user. On the other hand, there is, surprisingly, a marked decrease in the tendency of the sliding wall to jam and get stuck. The reason may be that the slanted grip handle gives rise to a force component in the direction towards the guiding surface that is necessary for the wall to slide along and this force component causes the guiding plane to become better defined and thus works against jamming. The best results were obtained with the upper end of the slanted grip handle pointing in the direction towards the open rest position.
In a variation of the arrangement described above, the wall that can be brought from a closed position to a removed position can be taken off; and for the removed position, the draft shield is provided with a holder to store the wall.
With the slanted grip handle, it is advantageous if the grip handle has a dual function in that the upper end of the slanted grip handle is opposed by a stop that defines one of the positions, particularly the open position. Thus, the previous arrangement of providing a separate stop on the side of the grip handle is no longer necessary, and the accessibility of the grip handle is improved.
In combination with the slanted grip handle described above, columns are provided which, in an advantageous arrangement, form the stop for the slanted grip handle and define one of the positions, particularly the open position.
In accordance with the aforementioned concept of a modular configuration to facilitate cleaning or the exchange of parts, it is also preferable for the columns to have a releasable kind of attachment on the draft shield.
It is particularly advantageous if the column and/or the protuberances, ledges, or similar formations are arranged around the part of the wall that is closest to the open position, providing an effective means against the tendency of the wall to tilt and get jammed when it is slid into the open position.
Further details of the invention are presented in the following description of examples of embodiments that are illustrated schematically in the drawing.